linux-kernel - Re: [PATCH drm-next v2 03/16] maple_tree: split up MA

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Message-ID: <Y+/ZW/8WXzrkQnUT@casper.infradead.org>
Date:   Fri, 17 Feb 2023 19:45:31 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Danilo Krummrich <dakr@...hat.com>
Cc:     airlied@...il.com, daniel@...ll.ch, tzimmermann@...e.de,
        mripard@...nel.org, corbet@....net, christian.koenig@....com,
        bskeggs@...hat.com, Liam.Howlett@...cle.com,
        matthew.brost@...el.com, boris.brezillon@...labora.com,
        alexdeucher@...il.com, ogabbay@...nel.org, bagasdotme@...il.com,
        jason@...kstrand.net, dri-devel@...ts.freedesktop.org,
        nouveau@...ts.freedesktop.org, linux-doc@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH drm-next v2 03/16] maple_tree: split up MA_STATE() macro

On Fri, Feb 17, 2023 at 02:44:09PM +0100, Danilo Krummrich wrote:
> \#define SAMPLE_ITER(name, __mgr) \
> 	struct sample_iter name = { \
> 		.mas = __MA_STATE(&(__mgr)->mt, 0, 0),

This is usually called MA_STATE_INIT()

> #define sample_iter_for_each_range(it__, start__, end__) \
> 	for ((it__).mas.index = start__, (it__).entry = mas_find(&(it__).mas, end__ - 1); \
> 	     (it__).entry; (it__).entry = mas_find(&(it__).mas, end__ - 1))

This is a bad iterator design.  It's usually best to do this:

	struct sample *sample;
	SAMPLE_ITERATOR(si, min);

	sample_iter_for_each(&si, sample, max) {
		frob(mgr, sample);
	}

I don't mind splitting apart MA_STATE_INIT from MA_STATE, and if you
do that, we can also use it in VMA_ITERATOR.